There are a variety of industrial processes that produce exhaust gases or other air streams that are entirely unsatisfactory from the standpoint of pollution control, both with respect to contaminants carried by the stream and unacceptable quantities of heat. In many of these processes, the contaminants consist primarily of organic solvents and other like materials that can be oxidized to form innocuous byproducts, water vapor and carbon dioxide. Direct release of the exhaust gas to the atmosphere is not permissible, due to Governmental regulations pertaining to pollution. Furthermore, a direct release of the exhaust gas stream would in most instances represent a highly undesirable heat loss materially reducing overall thermal efficiency.
Recovery of heat from the exhaust gases of industrial processes has frequently been effected, using various forms of heat exchangers. A rotary heat exchanger has been used for this purpose; examples are provided in Ljungstrom U.S. Pat. No. 1,586,816, Karlsson U.S. Pat. No. 2,680,008, and Dravnieks U.S. Pat. No. 3,733,791. These rotary heat exhangers can be quite effective in removing and recovering heat from industrial exhaust gas, but do not remove solvents and other contaminants.
In those instances in which removal of both heat and contaminants is required, it has been customary to provide for treatment of the exhaust or other gas in two separate stages, one for heat exchange and one for contaminant removal, as disclosed in Wenner U.S. Pat. Nos. 3,780,498 and 3,883,326. It has also been known to provide a catalytic cleaner or scrubber for removing contaminants from an air stream, as exemplified by Hirao U.S. Pat. No. 3,607,133, which converts carbon monoxide to carbon dioxide in an air stream, but incorporates no provision for heat exchange, or as exemplified by Cole U.S. Pat. No. 3,641,763 where both conversion and heat exchange are accomplished.